Underground mining is a complex operation whose goal is to extract as much resource as possible at the lowest possible cost. For example, in many mines, a network of rooms and pillars is carved out to maximize the amount of extracted ore while maintaining adequate roof support in order to avoid cave-ins.
Conventional mining techniques call for vehicles to haul loads of ore through underground passageways from the currently active section of the mine to the extraction point. Load-haul-dump vehicles scoop up several tones of ore and drive this to a common dump location. Sometimes the ore loads are dumped into larger haul trucks and driven along a main passageway to the surface. As mining progresses, the transport vehicles are required to travel ever longer distances to pick up the ore and bring it back. These transport vehicles must travel the same route many times and for the most part, this is done manually, either with a driver on the vehicle or more recently through tele-operation. Driver safety, operator fatigue, labour costs, and the cyclic nature of this task are all motivations to seek a solution to automate the process of driving these transport vehicles back and forth between the pick up and drop off points. Moreover, from a cost perspective, it would be advantageous to be able to accomplish this automation with requiring that infrastructure be installed throughout the mine, but rather by limiting the technology to the addition of equipment to the vehicles themselves and equipment associated with safety measures.
If reliable methods can be developed to automate the entire load-haul-dump sequence it will have an overall positive effect on mine safety and productivity. In the present invention the inventors are concerned only with methods for automating the hauling (or tramming) process, not loading/dumping. In the present invention the term “autotram” will refer to automated tramming or hauling. One of the key challenges of autotramming is that the global positioning system (GPS) is not available underground and thus the automation solution cannot rely on having good positioning information provided from this (external) system.
The earliest implementations of autotram borrowed ideas from automated-guided-vehicles by outfitting the mine with tracks, magnetic strips, or light-ropes that could be used to allow a vehicle to find its way down the passageways. Although these solutions were partially successful, installing the track/strip/light-rope infrastructure was very expensive and it was highly onerous to change the route as the infrastructure had to be altered. U.S. Pat. No. 5,530,330 issued to Baiden et al., for example, discloses a tramming system wherein the vehicle follows a light-rope installed along the passageway. It became clear over time that systems that could enable autotramming without infrastructure would be much cheaper to produce and maintain.
U.S. Pat. No. 5,999,865 issued to Bloomquist et al. discloses an autonomous vehicle guidance system that could be used to guide a self-propelled vehicle through passageways without infrastructure. It specifically considers self-propelled mining equipment in underground passageways. The system disclosed is comprised of a signal generator for bouncing signals off walls, a receiver for receiving the return signals and determining the distance to the side walls of the passageway, a storage device containing a set of interlinking nodes that represent at least one path through the passageway environment (each node contains steering information), and a processor to compare the side wall distances and steer the vehicle according to the steering information in the interlinking nodes.
The set of interlinking nodes is described as representing the topology of the passageway environment (e.g., straight, dead end, left corner, four-way intersection). The links indicate the connections between various passageway sections. Hence, the steering information that is said to be contained in the interlinking nodes is discrete in that it only directs the vehicle at a high-level whether to go straight, turn left, or turn right at each intersection. The lower-level task of steering to avoid hitting the walls is left to a reactive scheme that tries to center the vehicle in the passageway based on the distances to the side walls determined by the receiver. It should also be noted that no metric information about the path (e.g., distances to various wall points or a local metric submap wherein the notion of distance is defined) is contained in the route representation, only the topology of the passageway.
In mobile robotics research, systems similar to this that rely entirely on classifying tunnel topology to navigate have been shown to not operate robustly due to inevitable misclassifications that occur in practice. Other disadvantages of the disclosed system include: it does not discuss how the vehicle speed will be controlled, it does not explain how to account for vehicle dynamics (e.g., vehicle inertia, hydraulic steering, and engine dynamics) when controlling the steering and speed, and it does not claim a teaching method for creating the graph that represents the layout of the passageway environment. Furthermore, much discussion is devoted to the higher-level functions of path-planning and traffic management, which are beyond the scope of the current application.
U.S. Pat. No. 6,694,233 issued to Duff et al. discloses a system for relative vehicle navigation. The patent has three independent claims relating to localizing a vehicle without infrastructure, guiding a vehicle along a route without infrastructure, and a type of nodal map that can be used for localizing without infrastructure. The patent clearly defines a nodal map as a topological representation of a walled (i.e., passageway) environment. No metric information (e.g., local metric submap) is contained in the nodal map structure. As discussed above, systems similar to this that rely entirely on classifying tunnel topology to navigate have been shown to not operate robustly due to inevitable misclassifications of topology that occur in practice. The method for guiding the vehicle describes a specific approach using active contours, or snakes, to automatically generate a path for the vehicle on-the-fly. This on-the-fly path-planning is beyond the scope of the current application.
World Intellectual Property Organization Patent No. 2004/085968 issued to Makela discloses a method and control system for positioning a mine vehicle. The patent claims a method of counting the number of wheel revolutions and multiplying by a factor to obtain the distance traveled by the vehicle. It also claims a means of correcting the multiplication factor when the diameter of the wheel changes, which is beyond the scope of the current application.
Based on the drawbacks related to navigating from a topological map, the current invention is comprised of an alternative system to guide, navigate, and control a mining vehicle operating in an underground passageway environment based on a geometric map representation. This system can help enable the overall goal of robust and reliable mine automation.